The types of window coverings known as venetian blinds are themselves well known in the art. Modifications to such venetian blinds are also known, and examples of same are discussed below.
U.S. Pat. No. 5,402,840 to Jortner et al. is directed to a venetian blind tilt divider. In this patent, slats of blinds are divided into upper and lower portions by the installation of a divider. The divider must be attached individually to each ladder chord. Each divider must be removed and reattached to reposition the divider vertically. This divider offers only a few changes of pitch of the slats.
U.S. Pat. No. 5,205,335 to Horton et al. is directed to a method and apparatus for opening a portion of a venetian window blind while selectively closing another portion. This patent is directed to a system for modifying existing venetian blinds so as to maintain a desired portion of window slats open while simultaneously maintaining the remaining portion in a closed position. A clip is used in this system. The divider must be attached individually to each ladder chord. Each divider must be removed and reattached to reposition the divider vertically. This divider offer only a few changes of pitch of the slats.
U.S. Pat. No. 4,940,070 to Warden is directed to a bifold privacy miniblind. In this patent, individual blinds are supported by a string ladder support system on each side. A second control cord must be added to an existing venetian blind. The vertical location of the division cannot be easily changed.
U.S. Pat. No. 5,845,691 to Gaines teaches a venetian blinds control system. In this system, the upper half of blinds can be rotated independently. A second ladder cord and control must be added to an existing venetian blind. The vertical location of the division cannot be easily changed.
U.S. Pat. No. 4,621,672 to Hsu teaches a mechanism for a window blind. The blind includes horizontal slats and a regulating mechanism. When the upper slats are opened, the lower slats can be closed and vice versa. A second ladder cord and control must be added to an existing venetian blind. The vertical location of the division cannot be easily changed.
U.S. Pat. No. 4,697,630 to Rude teaches a tilt mechanism for venetian blinds. In this patent, a tilt mechanism uses band brakes having ends, and ladder cords being attached to these ends. This apparatus does not split the blind into upper and lower portions.
U.S. Pat. No. 5,119,868 to Werner teaches a venetian blind with a three-position tilt adjustment. In this patent, the slats are divided into upper and lower sections, the tilt of the slats being separately adjusted for each section. A second ladder chord and control are required. The vertical location of the division cannot be easily changed.
U.S. Pat. No. 1,229,523 teaches an adjustable closure for a window using bearings and flexible supporting guides. This apparatus differs significantly from applicant's invention.
It remains a problem in the art, however, to provide a venetian blind adjustment device which is easily attached to existing Venetian blinds, which can be replaced vertically without having to remove the device from the ladder chords, and which provides an adjusting divider so that two different portions of the venetian blinds can be adjusted differently.